Process for introducing a hardening sulfuric acid electrolyte into battery cells

Abstract

A process for introducing a hardening sulfuric acid electrolyte into battery cells at a sulfuric acid density of between 1.20 and 1.31, comprises the steps of combining (A) sulfuric acid, optionally together with up to 3% by weight of suspended silica; (B) a suspension of 6-12% by weight of silica in water; and (C) a water-in-oil emulsion of a polymer polyelectrolyte, in such proportions that the resultant mixture has concentrations of 3-5% by weight of silica and 0.1-1.0% by weight of polymer, and a sulfuric acid density of from 1.20 to 1.31, and intensively mixing the resultant mixture of components A, B and C at a mixing energy of 1-10 kJ/m 3 , whereby inversion of the mixture to an oil-in-water emulsion is initiated; and then immediately filling the mixture into battery cells. The starting components A, B, and C can be stored for a prolonged period. After leaving the mixer, the mixture hardens after about 120-180 seconds.

What is claimed is: 
     
       1. A process for introducing a hardening sulfuric acid electrolyte into battery cells at a sulfuric acid density of between 1.20 and 1.31, which comprises the sequential steps of: (A) combining three initially separate stable components, wherein said components are (i) sulfuric acid at a concentration of 50-80% by weight;   (ii) a suspension of 6-12% by weight of silica in water; and   (iii) a water-in-oil emulsion of a polyelectrolyte which is a polymer or copolymer of acrylamide having a weight average molecular weight of at least 1,000,000 daltons, wherein said emulsion has a polymer content of 20-60% by weight, a density of ρ=1.03±0.02 g/ml and a viscosity of η=300±100 mPa.s,      in such proportions that the resultant mixture has concentrations of 3-5% by weight of silica and 0.1-1.0% by weight of polymer, and a sulfuric acid density of from 1.20 to 1.31;   (B) intensively mixing the resultant mixture of components (i), (ii) and (iii) at a mixing energy capable of initiating inversion of the mixture to an oil-in-water emulsion; and   (C) immediately filling the mixture into battery cells while the latter are alternately subjected to a higher and a lower pressure.   
     
     
       2. The process as claimed in claim 1, wherein the lower pressure is a vacuum. 
     
     
       3. The process as claimed in claim 2, wherein air is admitted to the battery cells up to atmospheric pressure each time after they have been subjected to a vacuum. 
     
     
       4. The process as claimed in claim 2, wherein a vacuum of 50-80 kPa is generated. 
     
     
       5. The process as claimed in claim 2, wherein the repeating frequency for generating the vacuum is between 0.2 and 1 Hz. 
     
     
       6. An electrolyte filling kit, suitable for use in preparing a hardening sulfuric acid electrolyte in battery cells, comprising in three separate containers: (A) sulfuric acid at a concentration of 50-80% by weight;   (B) a suspension of 6-12% by weight of silica in water; and   (C) a water-in-oil emulsion of a polyelectrolyte which is a polymer or copolymer of acrylamide having a weight average molecular weight of at least 1,000,000 daltons, wherein said emulsion has a polymer content of 20-60% by weight, a density of ρ=1.03±0.02 g/ml and a viscosity of η=300±100 mPa.s.   
     
     
       7. The kit as claimed in claim 6, wherein in component A, said sulfuric acid is admixed with not more than 3% be weight of suspended silica. 
     
     
       8. The kit as claimed in claim 7, wherein said silica content is in the range of 1.3-1.5% by weight of the first starting component A. 
     
     
       9. The kit as claimed in claim 6, wherein the silica content is about 8% by weight in the second starting component B. 
     
     
       10. The kit as claimed in claim 6, wherein the polymer content in the emulsion is about 40% by weight in component C. 
     
     
       11. The kit as claimed in claim 6, wherein the silica used is pyrogenic SiO 2 . 
     
     
       12. The kit as claimed in claim 11, wherein silica of the hydrophilic type is used. 
     
     
       13. The kit as claimed in claim 12, wherein silica of the hydrophobic type with surfactants as an additive is added to the hydrophilic silica.